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Linux Command Line Essentials Every Developer Should Know
A practical reference for the Linux commands used daily in development — file system navigation, permissions, process management, text processing, and networking.
9 min read
The Linux command line is the universal interface for servers, containers, CI pipelines, and development environments. Whether you're SSH'd into a production server at 2am or debugging a Docker container, fluency with these commands is the difference between confusion and confidence.
Navigation and file management
# Navigate directories
pwd # print working directory
cd /var/log # absolute path
cd .. # up one level
cd - # go back to previous directory
cd ~ # home directory
# List files
ls # basic listing
ls -la # long format + hidden files
ls -lh # human-readable file sizes
ls -lt # sort by modification time (newest first)
# Create, copy, move, delete
mkdir -p path/to/dir # create directory + parents
cp -r source/ dest/ # recursive copy
mv oldname newname # rename or move
rm -rf directory/ # delete directory and contents (irreversible!)
touch file.txt # create empty file / update timestamp
# View and navigate files
cat file.txt # print entire file
less file.txt # paginated viewer (q to quit, / to search)
head -n 20 file.txt # first 20 lines
tail -n 20 file.txt # last 20 lines
tail -f /var/log/app.log # follow log in real time
File permissions
Linux permissions are expressed as three sets of read/write/execute bits for owner, group, and others:
-rwxr-xr-- 1 alice devs 4096 Apr 8 10:00 script.sh
Reading the permission string: -rwxr-xr--
-— file type (d = directory, l = symlink)rwx— owner: read, write, executer-x— group: read, execute (no write)r--— others: read only
chmod — change permissions
# Symbolic notation
chmod u+x script.sh # add execute for owner
chmod g-w file.txt # remove write for group
chmod o=r file.txt # set others to read-only
chmod a+r file.txt # add read for all (a = all)
# Numeric (octal) notation
chmod 755 script.sh # rwxr-xr-x (common for executables)
chmod 644 file.txt # rw-r--r-- (common for files)
chmod 600 ~/.ssh/id_rsa # rw------- (required for SSH keys)
chmod 700 ~/.ssh/ # rwx------ (required for .ssh directory)
Use our Chmod Calculator to build permission strings visually and understand what each octal value means.
Searching and text processing
# Find files
find /var/log -name "*.log" # find by name
find . -name "*.ts" -newer package.json # files newer than package.json
find . -type f -size +10M # files over 10MB
find . -name "node_modules" -prune # exclude directories
# Search file contents
grep "error" app.log # search in file
grep -r "TODO" ./src # recursive search
grep -i "error" app.log # case-insensitive
grep -n "error" app.log # show line numbers
grep -v "DEBUG" app.log # lines NOT matching
grep -E "error|warning" app.log # regex: error OR warning
# Stream text processing
cat access.log | grep "404" | wc -l # count 404 errors
cat data.csv | cut -d',' -f1,3 # extract columns 1 and 3
cat file.txt | sort | uniq # sort and deduplicate
cat file.txt | sort | uniq -c | sort -rn # count occurrences, sort by frequency
awk — field-based processing
# Print specific fields (tab-separated by default)
awk '{print $1, $3}' file.txt
# Process CSV (comma-separated)
awk -F',' '{print $2}' data.csv
# Sum a column
awk -F',' '{sum += $3} END {print sum}' data.csv
# Print lines matching a pattern
awk '/ERROR/ {print $0}' app.log
sed — stream editor
# Replace text
sed 's/foo/bar/' file.txt # replace first occurrence per line
sed 's/foo/bar/g' file.txt # replace all occurrences (global)
sed -i 's/foo/bar/g' file.txt # in-place edit (modifies the file)
# Delete lines
sed '/^#/d' file.txt # delete comment lines
sed '5,10d' file.txt # delete lines 5-10
# Print specific lines
sed -n '10,20p' file.txt # print lines 10-20
Process management
# View running processes
ps aux # all processes with details
ps aux | grep nginx # find nginx processes
top # interactive process viewer
htop # better interactive viewer (if installed)
# Process control
kill PID # send SIGTERM (graceful)
kill -9 PID # send SIGKILL (force kill)
pkill nginx # kill by name
killall node # kill all matching processes
# Background jobs
command & # run in background
jobs # list background jobs
fg %1 # bring job 1 to foreground
nohup command & # run immune to hangup (survives logout)
# System resources
free -h # memory usage
df -h # disk space usage
du -sh /var/log/ # directory size
lsof -i :3000 # what's using port 3000
Networking commands
# Connectivity
ping google.com # test connectivity
curl -I https://example.com # HTTP headers only
curl -o file.zip https://example.com/file.zip # download file
wget https://example.com/file.zip # alternative downloader
# Inspect connections
ss -tulpn # listening ports and processes
netstat -tulpn # alternative (older systems)
lsof -i :80 # what's on port 80
# DNS
dig example.com # DNS lookup
dig example.com MX # MX records
host example.com # simple DNS lookup
nslookup example.com # interactive DNS query
SSH and remote access
# Connect to a server
ssh user@server.com
ssh -p 2222 user@server.com # non-standard port
ssh -i ~/.ssh/id_rsa user@server.com # specific key
# Copy files
scp file.txt user@server.com:~/ # copy to remote home directory
scp user@server.com:~/file.txt . # copy from remote
scp -r ./dist user@server.com:~/app/ # recursive copy
# SSH tunneling (port forwarding)
ssh -L 5432:localhost:5432 user@server.com # tunnel remote DB to local port
Generate SSH key pairs for secure authentication with our SSH Key Generator.
Environment and shell
# Environment variables
export API_KEY=abc123 # set for current session and child processes
echo $API_KEY # print variable
env # list all environment variables
printenv PATH # print specific variable
unset API_KEY # remove variable
# Shell history
history # list previous commands
!! # repeat last command
!grep # repeat last grep command
Ctrl+R # reverse search history (type to search)
# Useful shortcuts
Ctrl+C # interrupt current process
Ctrl+Z # suspend to background
Ctrl+L # clear screen (same as clear)
Ctrl+A # jump to start of line
Ctrl+E # jump to end of line
Ctrl+U # clear line before cursor
Pipes and redirection
# Pipes — chain commands
ls -la | grep ".log" | wc -l
# Redirect output
command > file.txt # overwrite file with stdout
command >> file.txt # append stdout to file
command 2> errors.txt # redirect stderr
command > all.txt 2>&1 # redirect stdout + stderr to same file
command &> all.txt # shorthand for above
# /dev/null — discard output
command > /dev/null 2>&1 # discard all output (run silently)
Useful one-liners for developers
# Find and replace in all files in a directory
find . -name "*.tsx" | xargs sed -i 's/OldComponent/NewComponent/g'
# Get public IP
curl -s ifconfig.me
# Monitor a file for changes
watch -n 2 "ls -la uploads/"
# Compress a directory
tar -czf archive.tar.gz ./directory/
# Extract a tar.gz
tar -xzf archive.tar.gz
# Show the 10 largest files in current directory
du -sh * | sort -rh | head -10
# Count lines of code by file type
find . -name "*.ts" | xargs wc -l | sort -rn | head -20
The command line rewards investment. Every command you learn becomes a building block for more powerful combinations. Start with navigation and grep, then add pipes, then awk — and you'll handle any text-processing task that comes your way.